Currently, magnetic media, such as hard disk drives are used to store (record) and retrieve (playback) multimedia content in Digital Video Recorders (DVRs). While a hard disk drive may be quite efficient at storing and playing back a single content stream, many limitations arise where two or more content streams require simultaneous access. Each stream contains data that is best accessed from contiguous locations within the hard disk drive.
Contiguous storage of such content allows faster access and reduces fragmentation. However, since the data from two or more streams is multiplexed and placed at random track locations within the hard disk drive, the read write (RW) head has to continuously move between different sections of the disk to read or write this data. Alternatively, if the content received from the multiple channels is stored within a single contiguous section or contiguous block of the disk. The data (content) from the first channel (A) and second channel (B) alternates within the single memory location (contiguous section or block of disk) creating a potentially serious fragmentation problem. This second mode of operation is typically within most disk subsystems wherein their host is blind to the internal geometry and organization within the disk.
The structure and operation of hard disk drives is generally known. Hard disk drives include, generally, a case, a hard disk having magnetically alterable properties, and a read/write mechanism including Read/Write (RW) heads operable to write data to the hard disk by locally alerting the magnetic properties of the hard disk and to read data from the hard disk by reading local magnetic properties of the hard disk. The hard disk may include multiple platters, each platter being a planar disk.
All information stored on the hard disk is recorded in tracks, which are concentric circles organized on the surface of the platters. FIG. 1 depicts a pattern of radially-spaced concentric data tracks 12 within a disk 10. Data stored on the disks may be accessed by moving RW heads radially as driven by a head actuator to the radial location of the track containing the data. The track-based organization of data on the hard disk(s) allows for easy access to any part of the disk, which is why hard disk drives are called “random access” storage devices.
Since each track typically holds many thousands of bytes of data, the tracks are further divided into smaller units called sectors. This reduces the amount of space wasted by small files. Each sector holds 512 bytes of user data, plus as many as a few dozen additional bytes used for internal drive control and for error detection and correction.